Dispersed pigment from organic carbonaceous earth and process for producing the same



Patente Feb. 27, E34

DISPERSED PIGMENT FROM ORGANIC CARBONACEOUS EARTH AND PROCESS FORPRODUCING THE SAME Leonard lP. Dove, Hinsdale, 111.

No Drawing. Application August 4, 1931 Serial No. 555,143

26 Claims.

This invention relates to the production of organic or carbonaceousearth colors in a dispersed or finely divided form for use in woodstains or for coloring other materials of a wide range and variety, thedispersion to a finely divided condition being accomplished without theessential aid of grinding or other mechanical attrition.

The present application contains subject matter in common with my priorapplications Serial Nos. 339,290 and 339,281, both filed Feb. 11, 1929,now Patents Nos. 1,877,748, dated Sept. 13, 1932 and 1,898,247, datedFeb. 21, 1933, respectively.

The raw materials employed in connection with the invention and to whichthe processes have been found to apply are generally known ascarbonaceous or organic earths. These materials are found in naturallyoccurring geologic bodies that have usually been subjected to longoxidation or action of the elements in the air, water or soils.

It has been found in my experiments that most of these organic earthsthat appear best adapted to treatment by my process are usually brown incolor, varying from blackish brown to reddish brown. When ground in oilymediums, these organic earths are usually translucent or semitransparentin distinction to mineral earth colors composed of oxides of iron ormanganese, clay or silicates which are more or less opaque.

Organic earth colors are commonly used where a depth or richness isdesired such as in wood stains, grainers and in certain printing inksOrganic earths are usually composed for the most part of carbon,hydrogen, and oxygen with smaller quantities of admixed clay, ash,sulphur, nitrogen and moisture or other inert earthy materials.

It is generally assumed that these organic earths originated from thedecay of plants resulting in coal-like, lignite-like or peat-like bodieswhich in turn may have become altered by action of the elements. Ageneric term of ulmic or humic has been applied to these organic earths,regardless of origin.

These earths appear to have. a further characteristic in common offorming brownish solutions or colloidal suspensions in water solutionsof alkalis or alkali salts either hot or cold. This test is found to bevaluable as an indication of the suitability of raw materials fortreatment according to the process about to be disclosed, although I donot wish to limit the materials to such as may react in this way andthis alkaline treatment is in no sense a limiting part of thisdisclosure.

Bituminous coal, lignite and peat when fresh usually show a limitedsolubility in alkaline solutions, but when subjected by long exposure tooxygen or air, moisture, etc., show a marked increase in the amount thatdissolves in alkaline solutions and also may be dispersed by my process.

Alkaline solutions of these organic earths have been prepared and usedas water stains and for coloring paper, etc. However, it is.evidentthatthe usefulness of this color is limited to applications where water isnot objectionable. This color cannot be used in lacquers, varnishes orother oily or non-aqueous mediums because of the water necessary forsolution or dispersion. It is equally evident that if a similar color isprepared after the methods disclosed in this invention that is easilydispersed without the aid of water and may be used in paints, lacquersand other non-aqueous media, such a color would be very useful and findwide application.

Organic earths have been powdered to a pigment form, usually ground bymechanical means to pass a screen mesh of 200 to 325 to the inch. Inthis pigment form they have found a limited application for tintingpaints, wood fillers, etc.

Alkaline solutions of organic earths are usually precipitated oragglomerated by acids, acid salts, alum, etc. Alkaline solutions oforganic earths when dried yield a shiny black or brownish black solid.This material may likewise be dispersed according to my inventionbyusing this alkaline treated material as raw material. However, it is notas satisfactory as untreated material since it contains more solublesalts which are uncolored and act as diluents.

It has been found in my experiments that the richness and depth of coloris increased tg a marked degree by dispersion or stating it another way,by reducing the particle size. It is believed that the particles afterdispersion are essentially colloidal or ultra microscopic in size as itis found that pigments produced by my method pass easily through thefinest screen, and remain suspended almost indefinitely in oily mediums,indicating virtually a solution.

Having designated the raw materials useful in applying this inventionand calling attention to the desirable properties imparted bydispersion, I will now disclose the procedure by which dispersion ispossible.

Four materials used in the proper sequence produce very satisfactoryresults. These are as follows:

1. A suitable raw material designated as organic earth either treatedwith alkali or untreated, or raw.

2. A medium, vehicle, solution or menstruum 1. Raw material Organicearth, coal-like, lignite-like or peatlike is selected with reference tothe final color desired, the color strength and the proportion ofdispersible matter present. This material is usually dried in one of themany known ways to reduce the moisture content 10% or less at atemperature below the charring temperature which in this case is foundto be less than 150 C. All

these earths appear to be hygroscopic and will take up moisture whenexposed to moist air. For this reason processing should followdryingrather closely. Moisture even up to 40% of the raw material doesnot interfere seriouslywith processing, but appears to lengthen the timenecessary for complete dispersion. Since it must be driven outeventually as it is not desirable in the finished material, it is bestto reduce it at first.

Grinding of the raw material to 200 mesh or finer hastens the reactionsand while not essential is advisable as a matter of economy.

2. Dispersing medium The solution or medium in which the actualdispersion is carried out is preferably made up of organic solvents thatcontain low percentages of water. Ordinary organic solvents meet allrequirements. Water interferes more with mixing of the solvents than itinterferes with dispersion. Considerable latitude in preparation of thedispersing medium is allowable. For simplicity and to avoid repetition,the preference is indicated below in the order I have found in myexperiments to give best results.

Alcohols: methyl (wood), amyl, higher alcohols.

Coal tar fractions: benzene, toluene, xylene, cresols, and creosoteoils.

ethyl, propyl, butyl,

Ethers of the glycols: (ethylene, diethylene and triethylen'e).

Esters: ethyl acetate, butyl acetate, amyl acetate, ethyl lactate, etc.

Petroleum hydrocarbons: rather than solid.

My experiments indicate that certain generalizations hold, although itis not desired to limit the practice to such generalizations, but theseare given merely as rough guides to practice.

It appears that mixtures of alcohols are better dispersing media than asingle alcohol. Mixtures of alcohols and lighter coal tar fractionsappear to be better than mixtures of alcohols alone. Most ethers of theethylene glycols are fairly effective mediums alone but even better whenmixed with alcohols and lighter coal tar fractions.

The eifectiveness of the dispersing medium is judged by the completenesswith which the or ganic earth will virtually all dissolve or disperse.

Thus in preparing a dispersing mediiun not only must price andavailability of the solvents be considered, but the behavior of theparticular organic earth in the dispersing medium as well. Thusproportioning of the organic solvents should follow experiments thatshow the best results.

Not wishing to limit the proportions or solvents except that they makegood suspensions,

lighter fractions that produces or aids the the following proportionshave produced good results and are cited as examples of efiectivesuspending media Formula 1. A mixture comprising 2 gallons of commercialmethyl or wood alcohol (acetone which is commonly present does notinterfere) 1 gallon benzol (benzene) 1 quart ethylene glycol mono ethylether Formula 2.

2 gallons commercial denatured grain or ethyl alcohol 1 gallon toluol(toluene) or xylol (xylene) Formula 3.

1 gallon methyl or denatured ethyl alcohol gallon creosote oil, shinglestain oil or the like.

It is understood that the above are given as illustrations of goodsuspending or dispersing media and to illustrate the general statementsabove that mixtures of solvents appear to be more effective than singlesolvents except possibly some of the ethers of the glycols which appearto suspend the organic earth well when used alone.

In cases where it is desired to recover the dispersing medium byevaporating and condensation by well known methods, it is highlydesirable to design the, dispersing medium in such a way as to allow thesolvents to evaporate at an even rate to avoid over taxing thecondensers.

In some cases the dispersing medium may be marketable with the color ina paste or semiliquid form. In such cases it is apparent that thedispersing medium must be chosen with reference to its compatibilitywith the use.

3. Acid electrolyte An acid electrolyte is desirable to accomplishefiective dispersion. Its action appears to be to lend an electriccharge to the particles and thus permanently separate them sufiicientlythat they will not again cohere to each other. Strong commercial mineralacids accomplish this dispersion. Sulphuric, hydrochloric and nitricappear to produce about equally good results. Sulphuric acid appears tobe preferable, however, as insoluble sulphates that may form are not soobjectionable as chlorides or nitrates. Acid anhydrides which areusually gaseous are effective as are also acid salts, while salts, suchas alum, are very slow and weak in their action. Since the object ismainly-one of charging the particles during certain stages, the acidelectrolyte is chosen rather for its quick efiect, price and residuethat is left in the color, rather than any action it may have chemicallyto change or vary the color.

4. Alkaline electrolyte After dispersion is accomplished by means of theacid electrolyte, for most purpo'ses it is desirable to neutralize theacid and restore the color to a virtually neutral condition. Here againthe choice of the alkali is controlled more by the product produced bythe interaction of the acid and alkali and whether such neutralizationproduct is desirable in the finished product rather than for anyspecific property of the alkali itself, since it is indicated that thechoice of alkali has little to do with particle size or color, butmerely removes the acid. Except for convenience due to difficulty infinishing and filtering to remove the acid, the acid may be removed bywashing with water. The color being essentially colloidal any methodthat uses filtration is almost certain to be troublesome.

Since the sulphates of both calcium and bar'ium are common constituentsof paints and paint materials, a hydroxide, oxide or carbonate of theseelements makes a very satisfactory neutralizing agent. In certain casesa neutral product that may be vaporized at relatively low temperaturemay be highly desirable, in which case hydrochloric acid might be usedto disperse the color and ammonia to neutralize the acid producingammonium chloride which could be driven off as a vapor.

The amount of alkali to be added is best proportioned to exactlyneutralize the acid present. In practice it is usually preferable to addaslight excess of alkali since such excess is seldom harmful and oftenassists later dispersion in oily vehicles due possibly to the formationof soaps with the oily acids.

Procedure As an example of the procedure in making dispersed organicearth colors, the following may be taken as typical, but, as statedbefore, not limited to exact proportions nor ingredients.

In a suitable tank, vat or container, I place 100 pounds of a dispersingmedium made up as follows:

Parts by volume Methyl or wood alcohol 2 Commercial denatured ethylalcohol 1 Mono-ethyl-ether of ethylene glycol 1 Xylene 1 Into this isstirred about 30 pounds of dry powdered organic earth, such as oxidizedor weathered lignite. After the organic earth is wetted and welldistributed through the liquid, 3 pounds of commercial concentratedsulphuric acid is slowly added while stirring is continued. Heat isevolved and the mixture gradually thickens to a rich brown, oil-likeliquid, gradually becoming thicker until nearly a paste-like consistencyis reached. Approximately one-tenth of the weight of the dry organicearth gives about the proper amount of acid to be added when the acid iscalculated on the pure acid basis. For instance, a mixture of halfsulphuric acid and half water by weight would contain only half acid andit would thus require approximately 6 pounds of such a mixture todisperse 30 pounds of organic earth.

The amount of acid to be added is that amount that gives the maximumdispersion or acts on the entire mass, leaving no lumps or raw untreatedmaterial. Since it appears that the acid is only important to break upor disperse the organic earth and does not react with the earth indefinite proportions, the amount is discretionary to the extent ofproducing the best dispersion. Since the finer the raw material isground the less acid necessary, it would appear that reasonably finegrinding might be more economical than to use,

calcium oxide should be added, calculated as. CaO. In the above example,assuming that three pounds of acid is used and this acid contains 95 percent of pure sulphuric acid, it will thus require 1.63 pounds of pure02.0 to neutralize the acid.

The lime may be added in the form of a thin slip made by moistening thelime with a little of the dispersing liquid and then stirring this slipinto the vat of color, mixing it thoroughly. At this stage the productis improved if the whole liquid mass is passed through one of theseveral mills on the market that rubs or smears the mass in order to getbetter contact of the alkali and shorten the time of neutralization.This may also serve to rub out or grind any earthy or nondispersiblematter that was contained in the original raw material.

The mixture generally thickens further on the addition of the alkali,reaching the consistency of a semi-solid, or heavy paste.

For certain purposes, after the alkali has completely acted, this pasteis ready for marketing or use. It is best to allow from twenty-fourhours to a week if possible for the alkali to act, although this timemay be shortened by grinding or rapidly mixing the mass.

In most cases the market may demand a dry powder, in which case thedrying of the neutral ized mass is the last stage in the process. Thisis accomplished most economically by drying in a closed or vacuum drierin which the vapors are drawn or forced through a condenser andliquefied to be used over and over, or the dispersing medium may bedriven off by applying heat by any well known method of drying.Temperatures should preferably be kept below 150 C. as incipientcharring starts at about this temperature.

After the mass is neutral and still in the paste form, oils, waxes, etc.may be mixed with the paste and then the whole mass subjected to vacuumdrying, leaving the color dispersed in the oil or other substance andremoving the lower boiling solvents used in dispersing the color.Mineral oil, naphtha, gasoline, in fact most any substance that iscompatible with the dispersing nifidium may be added before drying, ifdesira e.

Aniline dyes or solutions of aniline dyes that have been made compatiblewith the dispersing medium may be added, preferably just before theneutralizing electrolyte, if colors that are variations of the brownbase are desired.

In a similar way inert earthy matter or fillers, Such as chalk, clay,silica or silicates, gypsum, plaster of Paris, pigments, etc. may beadded at any suitable stage of manufacture, should such materials bedesirable.

In certain cases, dyes in water solutions may be added to the colorduring the manufacture, so long as the water from the dye solutions doesnot predominate in the liquid used for dispers- The acid electrolyte maybe added directly to the raw material if desired, the order not beingessential except to be present to insure dispersion at the proper time.

It will be understood that the order of steps may be varied if desiredwithout departing from the spirit of the invention, although the orderherein set forth is preferred. It will also be understood that theneutralization of the dye may be omitted if an acid dye is desired.

What I claim is:

1. Aprocess of producing chemically dispersed dyes, which comprisesmixing a humic dye material normally insoluble in the common organicsolvents with an organic solvent containing a mixture of an alkyl etherof the ethylene glycols and an alcohol, and a concentrated mineral acid,then neutralizing the acid.

2. A process of producing chemically dispersed dyes, which comprisesmixing a humic dye material normally insoluble in the common organicsolvents with an organic solvent containing a mixture of an alkyl etherof the ethylene glycols and benzene, and a concentrated mineral acid,then neutralizing the acid.

3. A process of producing chemically dispersed dyes, which comprisesmixing a humic dye material normally insoluble in the common organicsolvents with an organic solvent and a concentrated mineral acid, thenneutralizing the acid and drying the neutralized mass to powder form.

4. A process of producing chemically dispersed dyes, which comprisesmixing a humic dye material normally insoluble in the common organicsolvents with an organic solvent and a concentrated mineral acid, thenneutralizing the acid and adding oil to the neutralized mass.

5. A process of producing chemically dispersed dyes which comprisesmixing a humic dye material normally insoluble in the common organicsolvents with an organic solvent serving as a dispersion medium,completing the dispersion by adding a concentrated mineral acid servingas an acid electrolyte, allowing the mixture to stand until thedispersion is completed, then adding an alkali to neutralize the acid.

6. A process of producing dyes which comprises chemically dispersing ahumic dye material normally insoluble in the common organic solvents, ina common organic solvent with the aid of a common commercialconcentrated mineral acid.

7. A dye comprising a chemical dispersion in a common organic solvent ofa humic dye material normally insoluble in the common organic solventwith the aid of a common commercial concentrated mineral acid.

8. A process of producing dyes as defined in claim 1'7, in which theorganic solvent is a member of a group consisting of alcohols andmembers of the benzene series of hydrocarbons.

9. A dye as defined in claim 7, in which the organic solvent is a memberof a group consisting of alcohols and members of the benzene series ofhydrocarbons.

10. A process of producing dyes as defined in claim 17, in which themineral acid is sulphuric.

11. A dye as defined in claim 7, in which the mineral acid is sulphuric.

12. A process as set forth in claim 6 wherein sufiicient alkali is addedto neutralize the acid.

13. A process as set forth in claim 6 wherein the organic solventcontains an alcohol.

14. A process as set forth in claim 6 wherein the organic solventcontains benzene.

15. A process as set forth in claim 6 wherein the organic solventcontains a homologue of benzene.

16. A process as set forth in claim 6 wherein the organic solventcontains creosote oil.

1'7. A process as set forth in claim 6 wherein the organic solventcontains a mixture of alcohols.

18. A process as set forth in claim 6 wherein t e organic solventcomprises a mixture of an alkyl alcohol and a coal tar fraction of thearcmatic series.

19. A dye as set forth in claim '7 wherein the organic solvent containsan alcohol.

20. A dye as set forth in claim 7 wherein the organic solvent containsbenzene.

21. A dye as set forth in claim '7 wherein the organic solvent containsa homologue of benzene.

22. A dye as set forth in claim '7 wherein the organic solvent containscreosote oil.

23. A dye as set forth in claim 7 wherein the organic solvent contains amixture of alcohols.

24. A dye as set forth in claim '7 wherein the organic solvent comprisesa mixture of an alkyl alcohol and a coal tar fraction of the aromaticseries.

25. A chemically dispersed dye comprising humic material, one of thecommon commercial concentrated mineral acids, an alkyl ether of theethylene glycols and an alcohol.

26. A chemically dispersed dye comprising humic material, one of, thecommon commercial concentrated mineral acids, an alkyl ether of theethylene glycols and benzene.

LEONARD P. DOVE.

